A large-scale boat or the like has two outboard motors equipped on the right and left of a transom board of a hull in some cases in order to obtain a large thrust. In the boat equipped with the two outboard motors, controlling steering angles of the outboard motors to different directions or controlling shift positions of the outboard motors to different shift positions enables not only normal turns to the right and left directions but also parallel movements in the right and left directions and turns at a fixed point to the right and left.
There is a known boat equipped with a joystick in addition to a steering wheel to allow a boat operator to easily perform steering such normal turns, parallel movements, and turns at a fixed point. For example, a maneuvering device for ship capable of freely perform the parallel movements and the turns at a fixed point by the operation of one operating unit through use of a joystick is disclosed in Patent Literature 1.
In the maneuvering device for ship disclosed in Patent Literature 1, an operation region of an operating lever of the joystick is divided into a first zone, a second zone, and a third zone, and steering angles and engine speeds of propellers according to the position and the quantity of turn of the operating lever are stored on a map for each divided zone. A maneuvering device for outboard motors can easily steer the ship by controlling the propellers to the steering angles and the engine speeds based on the map according to the position and the quantity of turn of the operating lever.